Catheters used in the medical industry, such as catheter products produced by Myelotec, Inc. for example, steer a distal end by manipulating stainless steel wires anchored into the distal tip of a plastic extrusion. FIG. 1 illustrates a catheter assembly 2 comprising extrusion 3 and distal end 4. Distal end 4 may include a lens and light carrying means, such as optical fiber, that facilitates a user viewing tissue and organs of a human, or animal, body. Applying tension to the proximal end 5 of either wire 6 causes distal end 4 of extrusion 3 to deflect in the direction of the wire 6, to which tension was applied, relative to the centerline of extrusion 3. For example, FIG. 2 illustrates that tension has been applied to rightmost steering wire 6R causing distal end 4 to deflect to the right. Similarly, applying tension to steering wire 6L (the figure does not illustrate this scenario for clarity) would cause distal end 4 of extrusion 3 to deflect to the left, or the opposite direction as that shown in the figure, but in the same plane as the movement depicted in FIG. 2.
In a two-wire configuration, such as the Naviscope® steerable catheter product line sold by Myelotec, Inc., a user may steer in only one plane at a time. Although the steering plane may be rotated 90° via a steering yoke and external collar from horizontal to vertical (See FIG. 3), compound movements, such as left-to-right sweeps while pointing downward, cannot be performed using two steering wires. As shown in FIG. 3, yoke bearing 8 receives rotation yoke 10 and rotation pin 11 protrudes through rotation slot 13. When housing halves 15 and 17 are mated together, collar 22 slides over the end of the mated housing halves and engages pin 11. Thus, a user gripping collar 22 can rotate extrusion 3 by turning collar 22. The extent of slot 13 limits the amount of rotation so that wires 6R and 6L remain untangled. When steering bearing 16 has received axle 18 of steering wheel 20, manipulating buttons 12 and 14 causes the distal end of extrusion 3 to deflect correspondingly. For example, pressing button 14 induces tension in steering wire 6R, which causes the distal end to deflect to the right as described above in connection with the discussion of FIG. 2. Similarly, pressing button 12 would induce tension in steering wire 6L and cause the distal end to deflect to the left.
A user may be able to rotate the steering plane (via collar 22) and re-point distal end 4 toward a desired location within a body, but only if the desired location falls within the area depicted in FIG. 7A. Should the location fall outside the possible steering planes (the point depicted with an X in FIG. 7A e.g.) the user must rotate housing halves 15 and 17 for viewing. However, since the optical fiber is attached to the housing, the image seen will be tilted with respect to the previous orientation of the image. Thus, there is a need for a catheter steering device that can steer a distal end of a catheter extrusion in multiple planes rather than one plane without causing image tilt as occurs when the distal end is rotated via the housing halves rather than being steered. Also, a need occasionally arises to cut bone without cutting a patient.